Ionization type voltage charging device



De. 24, 957 M. J. COHEN 2,817,776

IONIZATION TYPE VOLTAGE CHARGING DEVICE Filed Oct 1, 1952 I FRO/096771456 5 INVENTOR.

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ATTORNEY IGNIZATION TYPE VOLTAGE CHARGING DEVICE Martin J. Cohen, Princeton, N. I... assignor, by mesne assignments, to the United States ofAmerica as represented by the Secretary of the Air Force ApplicationOctober 1, 1952, Serial No. 312,584 6 Claims. (Cl. 310-3) This inventionrelates to converting the energies of nuclear and other high energyradiations into electrical.en-

ergy and more particularly to an improved ionization type voltagecharging device or generator.

Heretofore ionization type voltage charging devices have been devised inwhich. the diflerential mobilities or difierential rates of diffusion ofthe particles of an ionized medium are utilized to achieve voltagecharging. These particles comprise electrons and positive ions'produced,for example, by subjecting an ionizable medium to, high energyradiation. A collector electrode immersed in the ;-n1edium receives bothan electron and an ion current.

For ordinary gases the electron current is several hundred times thepositive ion current. Thus the electrode charges principles outlinedabove is greatly improved by utilizing a magnetic field to control therelative magnitudes of elec- Y tron and positive ion currents collectedby each electrode immersed in the medium. A further feature of theinvention is directed to selectively ionizing a portion of the ionizablemedium. By ionizing only a portion of the medium in a region adjacentone of the electrodes, it will be shown that some free electrons tendingto flow toward and be collected by the remaining electrode attach tomolecules of the medium and form relatively slow moving negative ions.Collection of such ions rather than more mobile electrons enhances thenet output voltage developed between the electrodes.

An object of the invention is to provide improved methods of and meansfor utilizing the energy of high energy radiations.

Another object of the invention is to provide improved methods of andmeans for generating electrical energy.

Another object of the invention is to provide improved methods of andmeans for utilizing the differential mobilities of free electrons andions to achieve voltage charging.

A further object of the invention is to provide an improved ionizationtype voltage charging device.

A still further object of the invention is to provide a more efficientionization type voltage charging device.

Another object is to provide an improved radioactive radiation detector.

The invention will be described in detail with reference to theaccompanying drawing in which:

Figure l is a schematic diagram of a first embodiment of an ionizationtype voltage charger, according to the invention;

Figure 2 is a schematic diagram of a second embodi- ;-'Patented Dec. 24,1957 2 mentof the. invention and in which selective ionization;..isemployed; and V Figure 3 .is a schematic diagram of a furtherernbodimentof the invention.

5 Similar reference characters are applied to similar elementsthroughout the drawing.

Referring to the drawing, Figure 1 shows a voltage charging device orgenerator which comprises a non-magnetic envelope ll containinganionizable medium 13 (such as argon .gas, hydrogen gas, helium, etc.)having a low coefficient of electron attachment. Alsocontainedin theenvelope 11 and mounted in a-spaced relation,in. the medium are a pairof electricallyconductive plane. electrodes 15 and 17 having theirrespective, axespreferably 5 normalto. each other. External to theenvelope. 11: a source 19 providing cold .high energy emission ismounted on a support 21. For the ensuing descriptionit will-.be assumedthat thesource materialis strontium abeta particle emitter. It isemphasized, however, that a ny 20 source material may be utilizedwhichproduces radiations capable of ionizing the gas 13. For example,materials which produce X-rays, deuterons, positrons, protons, fissionfragments, neutrons, ultra-violet rays, or cosmic rays are satisfactoryand may be employed. either, separately or in combination to ionize thegas.

Initially the electrodes 15 and 17 and the gas 13 are at the samepotential. However, beta particles radiatedby the. source 19 collidewith the gas molecules to ionize tihe gas and produce ion pairscomprising free electrons and positive ions. Since the electron currentnormally .,is ;sev-

eral .hundred times the ion current each electrode, 15 and '17, chargesto a negative potential and continues to charge negatively until anegative potentialis reached at which the free electrons comprising theelectron currentt are repulsed at such a rate that the electron andpositive ion currents flowing to each electrode are equalized.

Ordinarily, if electrodes 15 and 17 are similarly sized and/ or shaped,the voltages to which the electrodes charge are equal hence there is nonet output voltage developed.

40 The directional how of thecharged particlesti. e., electrons andpositive ions), however, may be controlled in accordance with onefeature of theinvention by subjecting the ionized medium to the effectsof a magnetic field. This magnetic field may be produced by anyconvenient means such as by a permanent magnet 23. The magnetic field isoriented such that the magnetic lines. of force 'are aligned parallel toone electrode, inthe present example the electrode 15, and normal to theremaining electrode 17. Thus, in instances in which it may be necessaryto utilize electrodes having substantially the same surface area, itwill be seen that the magnetic field controls the electron and positiveion current flow such that electrode 17 receives a much greater thannormal number of electrons and charges to a potential substantially morenegative than the negative potential to which electrodejl5 charges. Theratio of electron diffusion in the direction of the magnetic field forcelines compared to.electron diffusion in a direction transverse theretomay be as large as 1000 to 1, hence an appreciable net output voltage isdeveloped. The energy of this electric potential may then be expended ina suitable load circuit 25.

Referring to Figure 2 of the drawing, a preferredem- ,bodiment of theinvention is shown. In this instance the net output voltage developedbetween electrodes 15 and 17 is enhanced by utilizing collectorelectrodes having materially different geometries. Thepoint-planearrangement illustrated is one of a number of possibleconfigurations which are suitable. The point electrode: 15 (for themoment neglecting the directional currentcontrol effects of the magneticfield) charges to a less negative voltage than does the plane electrode17. fThis is true because a smaller negative charge 'on electrode 15will repel an approaching electron and cause it to miss electrode 15.The same negative charge on the larger .area electrode 17 may notprevent the electron from landing thereon. Since the control of themagnetic field is such that more electrons are directed to electrode 17than are directed to electrode 15, it will be seen that electrode 17, asshown, preferably possesses the greater surface area for electroncollection. If the converse condition were true, i. e. theconfigurations of electrodes 15 and 17 were transposed, the usefuloutput voltage developed by the instant apparatus would be appreciablyless.

According to a further feature of the invention the net output voltagedeveloped by the apparatusof Figure 2 may be further enhanced byselective ionization of the gaseous medium 13. This isefiected byproportioning and positioning the radiation source 19 to ionize only aportion of the gas 13. In order that the useful output voltage beenhanced rather than diminished the ionization region 27 is selected tobe adjacent electrode 17. As described above the free electrons andpositive ions produced by the ionization flow toward both electrodes.Since electrode 17 is closely adjacent region 27, free electrons andpositive ions flowing thereto are readily collected. However, electronsflowing toward electrode 15 have a relative longer distance to traversewithin the envelope before collection. A portion of these electronscollide with and attach to gas molecules in the un-ionized regions inthe envelope 11. This electron attachment reduces the number of freeelectrons flowing toward electrode 15 and causes the formation of acorresponding number of relatively slowly moving negative ions. Sincethe mobility of the negative ions thus formed is considerably less thanthat of free electrons, it is seen that electrode 15 charges negativelyat a slower rate thereby increasing the net output voltage derived.While electron attachment is desired for the reasons described above, anionizable medium having a low coefficient of electron attachment ispreferred. If a high coefiicient of electron attachment gas is used,although electrode 15 charges to a potential less negative than before,electrode 17 also charges to a less negative voltage whereby thepotential difference between electrodes 15 and 1'7 is reduced ratherthan enhanced. Also, to further improve the operation of the device, thematerial from which electrode 17 is formed preferably is different fromthe material of electrode 15, the material from which electrode 17 isformed having a greater affinity for electron collection (i. e., thework function of electrode 17 is lower than the work function ofelectrode 15).

Referring to Figure 3, a further embodiment of the invention is shown.The ionizable medium 13 in this example is contained within a hollowelectrically conductive non-magnetic toroid 29 and comprises aradioactive gas such as tritium which is capable of selfionization.immersed in the medium 13 are a plurality of disk shaped electrodes 31,33, 35, and 37. These disk shaped electrodes are insulated from thetoroid and are disposed at different angular positions around thetoroid. A magnetic field is produced having magnetic lines of forcewithin the toroid transverse to the disks by supplying current from asource 39 to a coil 41 wound about the toroid. The magnetic fieldstrength may be controlled by some suitable means such as apotentiometer 43 in shunt with the source 39.

The apparatus shown in Fig. 3 operates substantially in accordance withthe principles described hereinbefore with respect to the devices ofFigs. 1 and 2. Because of its radioactive nature the gas 13 ionizes andproduces free electrons and positive ions. Under the control of themagnetic field, these charged particles are collected in differentamounts by the inner surface of the toroid 29 and by the disk electrodes31, 33, 35, and 37. The disks preferably are connected together andcharge to a potential different from the potential to which the toroidAlso contained within the toroid 29 and I charges. The net outputvoltage again may be utilized to supply current and energy to a desiredload or utilization circuit. For purposes of simplicity only four diskshave been illustrated as immersed within the medium. It will berecognized however that any number of such collector electrodes may beemployed, the number of electrodes used depending, for example, on thedimensions of the toroid, the particular gas used, and the pressure ofthe gas. Also, it is pointed out that, if desired, selective ionizationmay be employed to further improve the operation and efficiency of theinstant device.

If the apparatus described with reference to either Figures 1, 2, and 3of the drawing is to be utilized as a radiation detector, it will beapparent that the sources of high energy radiations of Figures 1 and 2may be omitted or the radioactive gas (tritium) of Figure 3 may bereplaced with a suitable non-radioactive gas and ambient radiations usedto provide charging. In the event that the apparatus is to serve as avoltage source, it may be desirable to place the source materialsillustrated in Figures 1 and 2 within the envelope, for example,supporting it on one of the collector electrodes.

The instant invention thus comprises improved ionization type voltagecharging devices, generators, or radiation detectors. The utilization ofa magnetic field for controlling the directional flow of chargedparticles toward differently oriented collector electrodes greatlyenhances the differential voltage obtainable therefrom. Also, thefeature of selective ionization further improves the operation andefficiency of the device. While the radiation sources have beenillustrated as comprising films or coatings it will be recognized thatthese sources may assume various other forms.

What is claimed is:

1. Apparatus for primarily generating electrical energy comprising, anenvelope containing an ionizable gaseous medium, a pair of spacedelectrodes immersed in said medium, said electrodes having axes normalto each other, a source of high energy radiation positioned tocontinuously ionize only a portion of said gaseous medium to produce acopious supply of free electrons and positive ions in a region adjacentone of said electrodes, means for producing a magnetic field fordirecting different quantitles of said free electrons and positive ionsto said electrodes to establish a direct-current electric potentialtherebetween, and means for utilizing the electric energy of saidpotential.

2. Apparatus as claimed in claim 1 wherein said electrodes immersed insaid medium have different surface areas.

3. Apparatus as claimed in claim 1 wherein one of said electrodes ismounted within said envelope transverse to the lines of force of saidmagnetic field and the other of said electrodes is aligned in thedirection of said lines of force.

4. Apparatus as claimed in claim 3 wherein said copious supply of freeelectrons and positive ions is produced in a region adjacent saidtransverse electrode.

5. Apparatus as claimed in claim 1 wherein one of said electrodes is apoint electrode and the other of said electrodes is a plane electrode.

6. Apparatus for primarily generating electrical energy comprising, anionizable medium capable of self-ionization, a pair of spaced electrodeseach having a longitudinal axis, said electrodes being positioned insaid medium so that the longitudinal axis of one electrode of said pairis transverse to the longitudinal axis of the other electrode of saidpair, and means for impressing a magnetic field on said ionizable mediumwherein the lines of force of said magnetic field are parallel to onlyone of 'said axes and a direct-current electric potential is establishedbetween said spaced electrodes.

(References on following page) References Cited in the file of thispatent UNITED STATES PATENTS Ohmart Dec. 7, 1954 6 OTHER REFERENCES ANew Electric Battery, published in The Electrician, Vol. 10, page 497,dated October 31, 1924.

